Two old football coaches, by chance, sometimes meet up at Baltimore Ravens training camp.

Jack Harbaugh and Gary Moeller.

Brothers-in-arms of gridiron battles past, now retired. Hair, greyer. Legs, gimpier. Voices, a tinge raspier. But still possessing the same fire for life, the same passion for a kid’s game.

“I really enjoy it when I go down to training camp and Jack’s there, and we can kick back and tell stories,” Moellersaid this week over the phone while visiting Lima, Ohio. “Jack’s a great storyteller. And he can go on and on and on. We have a great time, reminiscing.”

About their careers. And, especially, about their boys.

John and Jim Harbaugh, and Andy Moeller.

Jack Harbaugh’s and Gary Moeller’s careers crossed paths for only four years, in the mid-1970s at the University of Michigan, as assistants under Bo Schembechler. That’s when their boys met. (And that’s Gary, left, and Jack, circa mid-’70s, at right.)

The trio became instant friends, and it was then – as children – that each began dreaming of a life in football, just like their dads.

Ever since, the sons’ paths have been crossing and criss-crossing far more frequently than their dads’ ever did, both on the field and off.

But never more significantly, or serendipitously, than next Sunday in Super Bowl XLVII.

John Harbaugh – Jack and Jackie Harbaugh’s oldest of three children – is the 50-year-old head coach of the Baltimore Ravens.

Jim Harbaugh – the middle child – is the 49-year-old head coach of the San Francisco 49ers.

Andy Moeller – Gary and Ann Moeller’s one son out of four children – is the 48-year-old offensive line coach of the Ravens, under John.

In a moment that has fate blushing and coincidence shaking its head, the Ravens – with John and Andy – will square off against Jim’s 49ers next Sunday in North America’s No.1 annual sporting spectacle.

Three boyhood, sports-loving friends – reunited four decades later on a football field in front of 72,000 in New Orleans and an expected North American TV audience of 120 million.

What are the odds?

In the mid-’70s as kids, the trio goofed off together, played backyard sports together, competed against one another in organized league sports, and got in trouble together – such as on one famous occasion when the Harbaugh boys unintentionally interrupted the high holy proceedings of a precisely scheduled Bo Schembechler Wolverine football practice, which aroused the hair-trigger wrath of the larger-than-life man they all worshipped then, and, in more than a few ways, still emulate now as coaches themselves.

While Schembechler (right, circa 1976) retired from the profession in 1990 and died in 2006, his coaching tree yet grows – a soaring, solid Savannah oak with gravity-defying branches snaking every which way.

A week from now the Bo tree adds a Super Bowl champion head coach from the pro ranks, whose last name is Harbaugh.

Many good yarns have been, and will be, spun about the Harbaugh brothers and this ‘Harbowl.’ This story chronicles the Harbaugh and Moeller offshoots on that tree, and how they began intertwining right from the get-go in Ann Arbor, Mich., starting in 1973.

Having grown up at about the same time, nearby, as a huge Michigan fan in Windsor, Ont. – just across the river from Detroit – I’m probably more familiar with this story than most. If there ever was a time to share it, it’s now.

* * *

John and Jim Harbaugh met Andy Moeller soon after their dad, Jack, left the University of Iowa football staff to join Schembechler’s at Michigan in ’73.

John was age 10, Jim 9, Andy almost 9.

Jack became the Wolverine defensive backs coach and served directly under Gary Moeller, then defensive coordinator.

So it all started with a Harbaugh working under a Moeller.

It was an enormous step up the coaching ladder for the elder Harbaugh, who had been relocating his family about every two years for a decade while moving up the ranks. Just six years earlier he’d been an assistant at Morehead State.

Now he was assisting one of the brightest, fieriest, exacting head coaches in all of college football – in the big-time. Schembechler’s ’70s teams were outstanding: 96-16-3 (.848).

This was the zenith of his 21-year career at Michigan, an era now principally remembered for the “Ten Year War” – when Schembechler’s Wolverines and Woody Hayes’ Ohio State Buckeyes annually fought tooth-and-nail for the Big Ten championship and Rose Bowl berth in their monumental, season-ending clash.

“Jack really fit in well with the Michigan coaches,” Gary said. “He’s very fundamental, just like his sons. You know, technique and all those things were important to him. And he could really communicate with the players, as well.”

Off the field, away from all that intensity, the Harbaugh and Moeller families became close.

Especially the kids.

“They’d hang out while going to practice, and watching practice,” Gary said. “John and Jim showed up with Jack, and Andy would come with me at times.

“We all really got to know one another better at the bowl games. They would spend lots of time together – all the kids did. We had a large staff of kids, really. On occasion, the families would get together in Ann Arbor too.”

The Harbaughs and Moellers lived in different areas of town. The youth football league fielded teams by district. John and Jim played on the Packers, Andy on the Wolverines.

So 1973 was the first time Jim competed against Andy in organized football.

As is always the case in youth football, many youngsters didn’t have a clue what to do. These three boys sure did, though.

“You’d see some kids with the facemask turned the wrong way,” Gary says, laughing. “They were just little kids. But our boys knew how to play the game, because they’d watched it so closely.

“They had fun playing against one another. I think they did in basketball, too. I know they were on opposite teams in that too.”

Over the next four years, John, Jim and Andy grew closer.

“They had the same group of friends as younger kids,” Gary said. “They saw one another quite a bit.”

By January 1977 the boys had entered their early teens. But that’s when the Moellers left Ann Arbor, for the University of Illinois hired Gary to be its head football coach.

The Harbaughs remained in “A-squared” until 1980, for seven years in all – by far the longest time the boys spent anywhere.

“We look back, and growing up mainly at the University of Michigan when they were in elementary school and junior high school, they loved sports, had a passion for sports,” Jack said in a teleconference call on Thursday with wife Jackie and daughter Joani. “They enjoyed being around the game.”

The famous story in Michigan circles is the day the Harbaugh boys lived to tell about interrupting a Schembechler practice.

Here they were playing catch off to the side of the field, as the Wolverines practised before some big game. But, as inevitably happens, the ball bounded the wrong way – onto the practice field, stopping proceedings.

Jim went out to fetch it. Schembechler went nuts, barking at Jack to get that something-damn kid off his something-damn field.

At Ravens’ training camp this past August, I asked John in an interview if that story were true.

“Absolutely! But who do you think was the one who sent Jim out there to get the ball?!” John said, laughing. “And Bo threw Jim off. I was the older brother. It was my prerogative.”

Gary Moeller laughs, too, at his boss’s reaction.

“Bo loved to holler at those young kids, because he liked to see them take off. They probably enjoyed it as much as they were scared about him getting on them.”

The way John set up Jim to get reamed by Bo speaks to their sibling rivalry.

It was intense. Not that you wouldn’t expect that from two highly athletic-minded brothers, born only 15 months apart.

Jim had a burning desire to not only compete in everything, but be the best in everything – and win at everything. As Jack said a couple of years ago in an NFL Films documentary about the family, a teacher once complained to him that little Jim competed too hard. Jack was appalled that an educator would actually want to drive that spirit out of his hyper-motivated son.

John, meantime, discovered at an early age that his younger brother possessed far more natural athletic ability that he did – which probably only further stoked his own competitive fires. No damn little brother of his was ever going to outdo him in anything, if he could help it.

Even if, as athletes, he couldn’t.

* * *

Both John and Jim played football in high school – John for four years at Ann Arbor’s Pioneer High, Jim for two years there before playing two more in Palo Alto, Calif., after dad Jack had left Michigan to work for Jack Elway (yes, John Elway’s dad) at Stanford.

John, a 6-foot defensive back, played college ball at Miami of Ohio – where Schembechler and Moeller had coached in the 1960s. Injuries kept him from playing much.

Jim, a 6-foot-3 quarterback, was an all-region player at Palo Alto High in his senior year, 1981. After having idolized Michigan’s option-wizard quarterback Rick Leach from 1975-78 (see video, above, of Jim congratulating Leach on a TD against Duke in 1977), Harbaugh as a high-schooler came to similarly admire Stanford’s starting quarterback at the time – one John Elway.

Just last week, Harbaugh was saying how he was still miffed he hadn’t been heavily recruited by the big colleges. Yet Michigan’s scholarship offer was no legacy gift, Gary Moeller said: “He was somebody that we definitely recruited.”

So back to Ann Arbor went Jim, as a freshman football recruit. Who joined him in that incoming class?

Andy Moeller, a star linebacker at Ann Arbor’s Pioneer High.

The Moellers had moved back to town in 1980, after Illinois fired Gary for going 6-24-3 (.227) in three years; Schembechler welcomed him back on his staff.

Reunited, old buds Jim and Andy both redshirted at Michigan in 1982, then saw spot action at their positions in 1983. Andy played quite a bit at inside linebacker in 1984, then started his final two years.

Jim started five games at QB in 1984 before breaking his arm, then broke out as one of college football’s most efficient, big-play quarterbacks in 1985 and ’86.

“Their junior and senior years, I think, they roomed together in a house – a bunch of guys lived in that house,” said Gary, who coached his son as Michigan’s defensive coordinator (see right). “When they both came back for a fifth year, they each went to separate apartments. They still got along well.”

In 1986, Harbaugh was everybody’s second-team all-American (behind Miami’s Vinny Testaverde) and finished third in the Heisman Trophy balloting.

Perhaps most importantly to Harbaugh, he became the 1980s version of his idol, Leach: A Michigan quarterback who dazzled with his arm and his feet, and who usually won the big games. Harbaugh even ran some option plays, out of both the I-formation and wishbone.

And, as Leach had done twice in the late ’70s, and as no Michigan quarterback has done since, in his senior season Harbaugh led the Wolverines to Pasadena by defeating Ohio State at Ohio State in a game for all the marbles. No small feat.

That day in 1986 says as much about Jim Harbaugh, the competitor, as anything ever could.

A week earlier, the Wolverines had been 9-0 and ranked No. 3 until a gutting, last-minute loss in their home finale to Minnesota.

Instinctively, Harbaugh surmised that his devastated teammates needed something to rally behind, with a trip to Columbus only days away and a Rose Bowl berth still there for the taking.

So Harbaugh shocked his teammates and – you better believe it – his coaches when he told the Detroit-area press corps on the Monday before that Michigan would beat Ohio State – guaranteed.

What did he just say?!! Yup.

No Michigan player under Schembechler had ever done anything remotely as bold. Yet the old man did not rebuke him. He, too, must have sensed the need.

Down in Columbus, Harbaugh’s guarantee was akin to spray-painting the entire city blue. Ohioans like Wolverines as much as Hugo Stiglitz liked Nazis in Inglorious Basterds. They now liked Harbaugh even less.

And he reveled in it.

The Buckeyes came out stoked, dominating the first half to take a 14-6 lead at the break. But in the second half, with tens of thousands of Buckeye fans either chanting his name in derision, or screaming their lungs out to try to drown out his offensive signals, Harbaugh didn’t flinch an inch.

In fact he was so poised, confident and self-assured in that second half, he continually made it appear as though he were struggling to yell out audibles to his teammates above the catcalls, which egged on the Ohio Stadium crowd to yell all the louder – which is exactly what he wanted.

Jim Harbaugh wasn’t audibling into anything. He intended to send those taunting Ohioans home not only with broken hearts, but hoarse throats.

Meantime, Andy Moeller helped to settle down a defence that had been shredded in the first 30 minutes both on the ground and, especially, through the air by quarterback Jim Karsatos and his favourite pass target, Cris Carter, the future Minnesota Vikings star.

In the end, Harbaugh had the third best passing day in series history (261 yards), Moeller and the defence stiffened, and Michigan won 26-24.

The Wolverines – led by their two co-captains, Jim Harbaugh and Andy Moeller – thus earned their first trip to the Rose Bowl in four years.

“Jim and Andy (Nos. 49 and 4, at right) provided excellent leadership that year,” Gary said. “They did that because they were hard-working kids. They saw that in other people all the way while growing up. They both worked hard. That’s the leadership you sometimes provide.”

* * *

Unsurprisingly, John, Jim and Andy all wound up pursuing careers in football.

Jim, of course, went on to have a solid 15-year turn as quarterback in the NFL – mainly with the Chicago Bears and Indianapolis Colts.

It was with the Colts that he earned the nickname “Captain Comeback,” for rallying the team to so many come-from-behind victories and taking it, in 1995, to within a whisker of reaching the Super Bowl.

Neither John nor Andy played football after college. Both went into coaching. Even before his NFL playing career ended, Jim started to coach, as a volunteer assistant for his dad at Western Kentucky.

While John and Andy got jobs more than once along the way thanks to dear old dad, or dear old dad’s connections, and while Jim’s fame as a player undoubtedly helped him when he launched his coaching career in earnest in 2001, the following must also be said.

Each paid his dues – starting out by working insane hours, doing the joe-est of jobs, for peanuts, at the lowliest levels.

They’ve earned this.

John has been head coach of the Ravens since 2008. Jim has been head coach of the Niners since 2011. Andy joined John’s first Ravens staff as assistant offensive line coach, then two years ago ascended to primary offensive line coach:

Jack reiterated this week that he is elated his sons chose to become coaches.

But wouldn’t a coach know better than anyone the life-sucking hours the profession demands, and thus want his sons to pursue something else?

Answered Gary Moeller about Andy:

“It’s what he wanted to do … I think you’re always happy when your kid is happy in his career. Yeah, we know the bad parts of the job, so you always worry about those, like you said – the long hours. But that’s part of it. And if you enjoy your work, it goes fast.

“It’s worked out well for Andy, obviously being part of the Super Bowl. It’s something that’s hard to get to. You can’t believe how many great players or coaches who have long careers who never even get into Super Bowls.”

John reportedly earned $4 million in 2012, Jim $5 million, and Andy probably about $200,000.

Asked what Schembechler would make of the trio’s coaching successes, Gary said:

“He would like how these guys have made it … He had great success himself, and to see that happen for these kids, it’s the same type of thing. He’d be very proud.”

* * *

Every now and then, I read a quote from John or Jim Harbaugh and chuckle.

Few besides a balding Michigan football historian like me probably ever suspects that some of their sayings, and actions, descend straight from one Bo Schembechler all those years ago.

Such as last year, when one of the Harbaughs – or maybe it was both – inspired his NFL players by telling them their one and only overriding concern had to be “the team, the team, the team.” That was a classic Schembechler creed; look it up on YouTube.

Or when Jim gets gruff with reporters in news conferences. Sometimes it sounds as though he’s actually impersonating Schembechler’s legendary snippiness.

Am I right about all these references, I asked John in that training-camp interview last summer?

“Yeah, you’re right. That’s exactly what it is, absolutely,” he said. “It’s Bo. And for us, too, it’s Jack. It’s our Dad. And our Dad was a part of that. We’ve heard Bo-isms since I was in fifth grade and Jim was in third grade, when we were at Michigan.”

Mantras don’t get your team to the Super Bowl, however. Good coaching does.

And one of the chief reasons the Harbaugh boys are winning, and winning big, at the NFL level – together they’ve been to five conference championship games in seven years, for goodness sake – is because they’ve also tapped into the bedrock Schembechler formula for winning football games.

Not his passé option-I offence, or his now archaic 5-2 slant defence. It’s something much more rudimentary, underneath all those X’s and O’s.

“I think we know what good football looks like,” John told me of his and Jim’s successes. “It’s irrespective of how you move the ball. It pertains to good football. Good, solid, field-position football.

“You don’t make mistakes. You play solid defence. You don’t turn the ball over. You get first downs, and you control the clock. And you can do that any way you want. You can do it throwing, you can do it running; you can do it blitzing, you can do it playing (zone) coverage.”

Thus, John said, his and Jim’s NFL success is “really founded on those principles … And for us, the principles remain the same – they’re written in stone. Methods can change, but the principles are in stone.”

Jack Harbaugh and Gary Moeller should have plenty more pride-swelling stories to regale each other with for years to come.